Automotive engines may have vacuum-utilizing systems (also referred to as vacuum consumption devices) coupled to the engine intake system, which may include a crankcase ventilation system for venting blow-by gases into the intake manifold, a fuel vapor purge system for purging fuel vapors from fuel vapor canister into the intake manifold, and a brake booster which utilizes vacuum from the engine intake to boost the force applied by the pedal (or other vacuum actuators). In order to regulate the flow of gases from each of the vacuum-utilizing system during various engine operating conditions, one or more aspirators may be coupled to each of the vacuum consumption devices to generate vacuum and increase the purging efficiency of the vacuum consumer.
One example approach to supply vacuum to a vacuum consumption device (e.g., a crankcase in a turbocharged engine) is shown by Pursifull et al. in U.S. Patent Application No. 2016/0341132. Therein, at least two valved aspirators are positioned in respective bypass passages around an intake throttle in order to generate vacuum for a brake booster. The valves controlling flow through the aspirators may be controlled separately to generate desired vacuum via the aspirators while also preventing throttle bypass during low intake air flow conditions.
The inventors herein have recognized a potential issue with the example approach described by Pursifull. As an example, separately controlling the at least two valves controlling flow through the aspirators may be complex and costly. Further, if other aspirators are present across the throttle (e.g., to generate vacuum for additional vacuum consumers such as a fuel vapor purge system), additional valves are needed to prevent throttle bypass, further increasing cost and complexity of the system.
The inventors herein have identified an approach to at least partly address the above issue. In one example, the issues described above may be addressed by a method including, during a first condition, opening a common aspirator shut-off valve to direct intake air through a first aspirator and a second aspirator each coupled across an intake throttle, and supplying vacuum generated by the first aspirator and the second aspirator to respective vacuum consumption devices as demanded. The method also includes responsive to a second condition, closing the common aspirator shut-off valve and supplying intake manifold vacuum to the respective vacuum consumption devices as demanded.
As one example, the first condition may include shallow intake manifold vacuum (e.g., as observed during boosted engine conditions) and the second condition may include deep intake manifold vacuum. In this way, air flow through each of the aspirators may be provided by opening the aspirator shut-off valve during shallow vacuum conditions where intake manifold vacuum is not sufficient to operate the vacuum consumers, while air flow around the intake throttle may be prevented by closing the aspirator shut-off valve during low air flow conditions, all with a single common aspirator shut-off valve. By doing so, system cost and complexity may be reduced.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.